A high-refractivity high-dispersion optical glass is highly demanded, and in particular, aspherical lenses formed of the above glass are indispensable as lenses for high-performance digital still cameras.
As a method for mass-producing aspherical lenses, there is known a precision press-molding method (which is also called “optical press molding method”). As a high-refractivity high-dispersion optical glass that is moldable by a precision press-molding method, a phosphate glass is known. While the phosphate optical glass is an excellent glass, it involves a problem that a glass surface is liable to be damaged during its precision press-molding.
As a non-phosphate glass having high-refractivity high-dispersion properties, glasses disclosed in Patent Documents 1 to 5 are known. All of these glasses have silica-containing compositions.